See this TurboTax support FAQ - https://ttlc.intuit.com/community/agi/help/where-do-i-correct-my-agi-in-turbotax-online/01/26311
Using TurboTax, it's not uncommon for IRS to reject your AGI amount even if it you have entered the correct amount.
In that case, you have to file by mail at the Post Office.
Sometimes AGI = zero will work.